1. Field of the Invention
The present invention relates to a rotary machine and an electrical vehicle using it and more particularly to a reluctance type rotary machine suitable for an electrical vehicle and an electrical vehicle using it.
2. Prior Art
Recently, a motor used for an electrical vehicle such as an electric car or a battery fork is required to be small-sized, light in weight, and highly efficient. Therefore, as a driving motor of an electrical vehicle, a brushless motor (reluctance motor) using 1) a permanent magnet or 2) reluctance is most suitable. Particularly, as compared with a permanent magnet type motor using a highly efficient permanent magnet, although a reluctance motor is slightly low in efficiency and torque, it is almost equal to a permanent magnet type motor using a ferrite magnet and has an advantage that there are no problems imposed such as dependence on temperature of the characteristics and demagnetization of the magnet.
A first conventional reluctance motor, for example, as described in Electric Society, June Issue, 1996, “Magnetic Field Analysis and Prototype Experiment of Flux Barrier Type Reluctance Motor Using Slit Rotor”, has a structure that a rotor is composed of a magnetic substance such as a silicone steel plate, and the plate is laminated in the axial direction, and several layers of non-magnetic slits are installed in the direction from the center of one magnetic pole (or may be called a salient pole) of the rotor to the center of another magnetic pole. By use of such a structure, the ratio Xd/Xq of the reluctance (Xd) at the magnetic pole center (or may be called salient pole center) to the reluctance (Xq) between the magnetic poles (or may be called between the salient poles) which is a most important factor of the reluctance motor can be increased, that is, the produced torque of the motor can be increased.
A second conventional reluctance motor, for example, as described in Japanese Patent Application Laid-Open 9-93885, uses a material that the ferromagnetic part and non-magnetic part coexist so as to ensure the mechanical strength which is a defect of a flux barrier type reluctance motor.
However, in the first conventional reluctance motor, although the ratio Xd/Xq of the reluctance (Xd) at the magnetic pole center to the reluctance (Xq) between the magnetic poles can be increased compared with a general reluctance type rotary machine, since there is a magnetic part in the outer periphery, leakage flux flows until it is saturated. Due to the leakage flux, Xq cannot be decreased sufficiently, and Xd/Xq cannot be increased, and the produced torque cannot be increased sufficiently. To decrease the leakage flux, it is necessary to reduce the thickness of the peripheral bridge. However, when the bridge thickness is reduced, a problem arises that the mechanical strength during high-speed running is not sufficient.
In the conventional second reluctance motor, since the rotor is integrated, the mechanical strength can be improved, though the magnetic permeability of the non-magnetic part cannot be reduced like that of air. Therefore, a problem arises that the leakage flux increases and the ratio Xd/Xq, that is, the produced torque cannot be increased sufficiently.